Also known as: Airspy HF+, Airspy HF plus, HF+ Discovery
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Airspy HF+ is a software-defined radio optimised for the HF and low-VHF bands, with very high dynamic range for receiving shortwave and weak low-band signals.1 Where the VHF/UHF Airspy R2 chases wide bandwidth, the HF+ chases the opposite goal: a narrow, exceptionally clean window on a crowded low band where a single strong broadcaster can otherwise desensitise the whole receiver.
Key takeaways The HF / low-VHF dynamic-range champion. The Airspy HF+ Discovery covers HF (to ~31 MHz) and a low-VHF window (60–260 MHz) with a narrow (~768 kHz), exceptionally clean capture — its polyphase harmonic-rejection mixer and high-resolution ADC survive a crowded shortwave band where cheaper receivers fold under overload. Pick it if you want shortwave or ham HF too, not primarily for scanning: GopherTrunk’s trunking targets (P25, DMR, NXDN) live in VHF/UHF, where an Airspy R2 or an RTL-SDR is the right radio. Receive-only, ~$170. Like every receiver it can’t decode AES encryption. See best SDR for GopherTrunk.
How it works
HF is a hostile band for a receiver: hundreds of powerful shortwave, broadcast-AM and amateur signals arrive at once, and the challenge is not sensitivity but not being overloaded by the strongest of them. The HF+ is built around that problem rather than around raw bandwidth:
- A polyphase harmonic-rejection mixer and a very selective front-end tuner suppress the images and harmonics that a simpler mixer would fold into the passband, so nearby strong signals do not create spurious responses.
- A high-resolution sigma-delta ADC and heavy oversampling deliver very high dynamic range — the headroom to hear a weak signal sitting next to a broadcaster tens of dB louder.
- The delivered capture is deliberately narrow (up to ~768 kHz for the HF+ Discovery), which is all a shortwave, marine or amateur channel needs, and keeps the in-band energy — and thus the demand on the ADC — small.2
The tradeoff is explicit: the HF+ will not give you the 10 MHz-wide slice an Airspy R2 does, because on HF that width would let in more strong signals than any front end could handle cleanly. It is receive-only.
Variants
- Airspy HF+ — the original, covering HF and a low-VHF window (60–260 MHz).
- Airspy HF+ Discovery — a smaller, refined revision with an improved preselector and even better close-in dynamic range; the current mainstream HF+ model.
Both target the same job. Against the alternatives, a basic RTL-SDR needs an upconverter or a lossy direct-sampling hack to reach HF at all and has far less dynamic range; an SDRplay RSP1A is a wideband 14-bit rival that covers HF continuously through GHz but is generally beaten by the HF+ on pure close-in HF dynamic range; and the older FUNcube Dongle is a narrowband receiver aimed more at satellite work.
Relevance to SDR
The HF+ is the receiver of choice when HF or the low VHF band is your target — shortwave broadcast, amateur SSB/CW, marine HF, ionospheric propagation study, or low-band utility monitoring — precisely because its dynamic range survives the crowded HF environment where cheaper receivers fold under overload.
For GopherTrunk this is more of a complementary tool than a core one: the land-mobile trunking systems GopherTrunk decodes (P25, DMR, NXDN, TETRA) live in VHF/UHF, where an Airspy R2 or an RTL-SDR is the right radio. GopherTrunk can drive the HF+ as a receiver, but its wideband-channelizer strengths don’t apply to the HF+’s narrow captures. Choose the HF+ when the low bands themselves are what you want to hear.
Where to buy
The current mainstream model is the Airspy HF+ Discovery. Airspy sells through its own distributor network, so Amazon stock is intermittent — the button below is a tagged search that resolves to the live listings rather than a single page that may be out of stock.
Airspy HF+ Discovery on Amazon →
If your target is really VHF/UHF trunking rather than the low bands, an Airspy R2 or an RTL-SDR is the better buy — see best SDR for GopherTrunk and, if you’re comparing against a handheld, police scanner vs SDR. Then get the software from the downloads page.
As an Amazon Associate, GopherTrunk earns from qualifying purchases — at no extra cost to you. It never changes what we recommend.
Sources
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Software-defined radio — Wikipedia, for background on the Airspy HF+ and HF-optimised, high-dynamic-range SDR receivers. ↩
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Airspy HF+ Discovery — Airspy, on the HF+ architecture, polyphase harmonic-rejection mixer, coverage and dynamic-range design. ↩
Frequently asked questions
Is the Airspy HF+ Discovery the right SDR for GopherTrunk?
Only if the low bands are your target. GopherTrunk decodes land-mobile trunking (P25/DMR/NXDN/TETRA) that lives in VHF/UHF, where an Airspy R2 or an RTL-SDR is the right radio. The HF+ Discovery is the pick when you also want shortwave, amateur SSB/CW or marine HF — its dynamic range is the best in class on a crowded low band. GopherTrunk can drive it as a receiver, but its wideband-channelizer strengths don’t apply to the HF+’s narrow captures.
Why choose the HF+ Discovery over an RTL-SDR with an upconverter for HF?
Dynamic range. On HF the challenge is not sensitivity but surviving dozens of strong broadcasters at once. The HF+ Discovery’s polyphase harmonic-rejection mixer and high-resolution ADC hear a weak signal next to a broadcaster tens of dB louder, where an 8-bit RTL-SDR plus a lossy upconverter or direct-sampling hack folds under overload.
How wide a capture does the HF+ Discovery give?
Up to about 768 kHz — deliberately narrow. That is all a shortwave, marine or amateur channel needs, and keeping the window small is exactly what lets the ADC deliver its very high dynamic range. It will not give you the 10 MHz-wide slice an Airspy R2 does.
Can it decode encrypted transmissions?
No. The HF+ Discovery is receive-only and GopherTrunk is a receive-only decoder — no SDR or scanner can decode AES-encrypted traffic.